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Thesis Proposal Mechanical System Redesign: Heat Recovery and River Heat Rejection

The Hospital for Special Surgery River Building New York, New York

Prepared For:

Dr. William P. Bahnfleth, Ph.D., P.E., Professor Department of Architectural Engineering The Pennsylvania State University

Prepared by: Maxwell S. Chien December 18th, 2007

Thesis Proposal Hospital for Special Surgery New York, New York

Maxwell S. Chien, Mechanical 2

Table of Contents

ExecuQve Summary Page 3

Building Overview Page 4

Mechanical Design ObjecQves Page 5

Mechanical Design Overview Page 6

Mechanical Design CriQque Page 7

Mechanical Proposal Topics Page 8

Breadth Proposal Topics Page 10

Projects Methods Page 11

Spring Semester Proposed Schedule Page 12

References Page 17



ExecuQve Summary

The HSS River Building, a part of the Hospital for Special Surgery campus on the Upper East Side of Manha>an, is an 88,245‐square‐foot building rising 190 feet above the FDR Drive highway. The River Building is an acute care facility containing primarily exam rooms, X‐ray rooms, doctor offices, and a rehabilitaPon gym on the second floor.

The mechanical system for the HSS River building is a constant air volume system (CAV) with heat pump water loop providing cooling and heaPng for the 100% Outdoor Air Handling Unit (AHU) and provides heat absorpPon and rejecPon to the terminal water‐to‐air heat pumps in occupant spaces on each floor.

This proposal will outline the topics, methods, and Pmeline that will be approached for the mechanical redesign and the structural and architectural breadth topics. The mechanical redesign proposal will replace the 100% OA AHU unit with one containing a heat recovery wheel. Also, the East River next to the building will be analyzed and used as a heat rejecPon source for the heat pump loop system.

In addiPon to the redesign of the air distribuPon system and heat pump system, two breadth areas will also be developed. The first breadth will look at the new mechanical equipments and its effects on the structural system of the building to see whether or not it can be downsized to save cost. The other area will be the architectural building façade to see whether or not reducing the 60% glass fenestraPon by solar shades or a different material will be the best opPon to lower internal thermal loads.

To analysis these topics, a schedule of the spring semester was created to organize research and allocate design hours for the thesis project. In the research phase, available products and previous projects from Cannon Design and other companies will be studied in order to gain familiarity and knowledge of the area of study. In the design phase, Trane Trace, a building energy modeling soaware will be used along with Microsoa Excel to calculate the necessary informaPon needed to determine whether or not the redesign is feasible and correct. Also, the architectural breadth will require renderings done in Photoshop and Autodesk Revit, a computer aided 3D soaware.



Building Overview

The HSS River Building is a twelve story 88,245 square feet building located in the Upper East Side of Manha>an. The building is used for acute medical care, containing primarily exam rooms, X‐ray rooms, doctor offices, and a rehabilitaPon gym on the second floor. The HSS River Building is designed to be on top of the FDR Drive highway, overlooking the East River. Figure 1 shows the locaPon of the building on the Upper East Side.

Inside the River Building, the project was designed as a core and shell, leaving the interior programming to the client’s request. The core and mechanical system were designed to use the least amount of space possible so that the client will be able to rent out the space. This being said, the HSS River Building’s mechanical system only takes up 1% of the rentable space available as all equipments are located in the penthouse and concealed in the plenum. Figure 2 shows the west elevaPon of the HSS River Building.

The building is supposed to be built on the Hospital for Special Surgery campus located between 70th and 71st Street and borders between York Ave and the FDR Drive. The campus is very dense containing (3) buildings within that block. The HSS River Building is designed to be built as an addiPon to the Caspary Building to extend over the FDR Drive. The building also has more than 50% of the facade containing glass on the north, south and east exposures and also straddles over the busy FDR Drive.

Unfortunately, the project was stopped at 100% Bid Documents to be redesigned at the request of the Owner.

Figure 1. LocaQon of the HSS River Building Figure 2. West ElevaQon



Mechanical Design ObjecQves

The mechanical system for the HSS River building is a constant air volume system (CAV) with heat pump water loop providing cooling and heaPng for the 100% Outdoor Air Handling Unit (AHU) and occupant spaces on each floor. The minimum outdoor air is brought in and mixed with the return air in each terminal heat pump unit serving each area. The main heat pump provides cooling and heating for the AHU is water‐to‐ water system where as the terminal units are water‐to‐air. The design of the mechanical system for the HSS River Building was developed from the following objecPves:

• Occupant Controllability • Energy efficiency • Space conservaPon • Reduce spread of contaminates

With these objecPves in mind, the HSS River Building uses mulPple terminal heat pumps which can simultaneously provide heaPng and cooling, providing occupant controllability of temperature for each serving space. To increase energy efficiency, the HSS River Building mechanical system uses a heat pump loop with a 100% air handling unit sized for the minimum outdoor air, reducing energy needed to condiPon a larger amount of outdoor air. Lastly, by sizing the duct penetraPons for the amount of outdoor air only and mixing the recirculaPon and outdoor air at the terminal end reduces the amount of space needed for the ductwork. By not mixing the return air with the outdoor air in the Air Handling Unit, the system prevents contaminates and air borne diseases to circulate throughout the enPre building.

In a heat pump system, there are two sets of temperature ranges for the heat pump to work efficiently. One set is called the load loop temperature and the other is the source loop temperature. In the HSS River Building, a steady temperature range of 90F to 100F is need for the source loop and 46F and 55F for the load loop for cooling. For heaPng, a range of 60F and 70F is needed for the source loop and 90F and 100F for the load loop. In order to maintain this constant temperature, a cooling tower and heat exchanger are used to reject and supply addiPonal heat to the system.

The HSS River Building was designed to also meet ASHRAE Standard 62.1‐2004 VenPlaPon requirements but did not meet all requirements set forth for ASHRAE Standard 90.1. These results were studied in Technical Assignment 1 – ASHRAE Standard 62.1‐2007 Ven>la>on Report and Technical Assignment 2 – Building and Plant Energy Analysis Report.



Mechanical System Overview

Air DistribuQon ‐ The HSS River Building provides 100% minimum outdoor air (OA) through the McQuay roof top unit bringing 14,000 CFM into the building. The OA is condiPoned by heaPng and cooling coils and ducted down to each floor. The outdoor air is mixed with the return room air by the terminal heat pump units in the plenum. The supply air is then conditioned again by the terminal heat pump unit. In order to provide thermal comfort, the AHU has an entering and supplying summer temperature of 95F and 57F respecPvely while the entering and supplying winter temperature is 0F and 92.5F respecPvely. The HSS River Building also contains (6) centrifugal roof up‐blast exhaust fans. They are used mainly for exhausPng air from toilet rooms and locker rooms. Other exhaust fans are used for exhausPng the exercise room on the 2nd floor and also for smoke purging all floors in case of a fire.

Heat Pump System

The mechanical system contains (3) water‐to‐water heat pumps to condiPon the 100% outdoor air and provides heat rejecPon and absorpPon for the (157) terminal water‐to‐air heat pumps serving the floors. The heat pump source and load loop system contains a mixture of water and 35% propylene glycol to prevent the loop from freezing. The (3) water‐to‐water heat pumps provides the entering water temperature needed for the terminal heat pump units to reject and absorb heat during cooling and heaPng seasons. This being said, the terminal heat pump units provides their leaving water temperature as the entering water temperature needed for the source loop for the (3) water‐to‐water heat pumps. This delicate balance is kept in check by a cooling tower and heat exchanger to reject or add more heat to the system to maintain constant temperature differences.

Heat AbsorpQon ‐ Steam

Con Ed, the uPlity provider for electricity for the HSS River Building also provides high pressure steam at 160 psi. The steam is stepped down from 160 psi to 80 psi and then down to 15 psi by two sets of Pressure Reducing Valves (PRVs). This low pressure steam (LPS) is then directed to the heat exchangers to provide heat to the heat pump source loop.

Heat RejecQon – Cooling Tower

When addiPonal cooling occurs, the heat pump loop load leaving temperature from each terminal heat pump will increase. This increase in temperature is rejected through the cooling tower to maintain the constant 90F entering temperature for the (3) heat pumps



serving the AHU. It is a closed loop system to minimize process fouling and also contains a steam basin heater to prevent spray water from freezing.

Mechanical System CriQque

Air DistribuQon CriQque

The air distribuPon of the HSS River Building can be seen as a saPsfactory system. The system does not use more space and materials than convenPonal AHU return systems where either a ducted return or open plenum is required to bring all the return air back to the AHU. The air distribuPon also does decently at isolaPng serving zones from each other, which is important in an acute medical procedure building to prevent cross contaminants as each return air is re‐circulated in each zone. But on the contrary, the mixture of outdoor air and room air is never exhausted in each serving zone but rather at negaPve pressure zones such as restrooms, lockers and the rehabilitaPon gym. This creates a posiPve pressure for every zone, possibly resulPng in cross contaminaPon into the negaPve pressure zones.

Another quesPonable design is the absence of heat recovery from the 100% OA AHU. As of now, the AHU is being condiPoned by the heat pump source loop, but it can be condiPoned by the exhaust air from the building with a heat recovery wheel. This topic will be discussed in the proposal.

Heat Pump System CriQque

The heat pump system in the HSS River Building is an effecPve system. The heat pump system requires less space and energy to heat and cool the space. It also allows for simultaneous cooling or heaPng in different zones of the building at the same Pme as the terminal heat pump simply reverses its refrigerant flow cycle to allow this. This is a great advantage dealing with the diversity in the building as it contains fully exposed ceiling to floor glass on every floor on the North, East and South side. This is a great feature for providing control for the occupants. Even though the heat pump system is very delicate in its coordinaPon of temperatures with the water‐to‐water heat pump serving the AHU and the water‐to‐air heat pumps serving each zone, the balance is maintained through controls and the cooling tower for heat rejecPon and heat exchangers for addiPonal heat. A potenPal concern of this system is the numerous amounts of terminal heat pumps concealed in the plenum on each floor that would need to be maintained throughout the year. This process will have to be done on premium Pme on weekends in order not to disturb the doctors and paPents on the weekdays.



Mechanical Proposed Redesign

The mechanical system for the HSS River Building was designed adequately for its purpose of reducing the spread of contaminates, providing controllability to the user, and reducing energy use. But as with any system, there can be alternaPve designs for improvement. The following proposal for redesign of the air distribuPon and heat pump system will be the topics of study for the spring 2008 thesis. Below are the proposed topics and a descripPon of how to approach each redesign.

Air DistribuQon System

The HSS River Building provides its occupants with a supply air that is made up of the minimum required outdoor air mixed with the exisPng room air. This outdoor air is brought in by the 100% OA AHU on the rooaop that uses energy to condiPon harsh winter and summer outdoor air to ideal comfort room temperatures. The River Building also contains (6) exhaust fans, exhausPng condiPoned air out of the building. This being said, the proposed alternaPve redesign is to provide condiPoning to the outdoor air temperatures by heat recovery from the exhaust. This system is commonly used with systems that use 100% OA AHUs.

This heat recovery process can be achieved by using an enthalpy wheel which condiPons the outdoor air by using the heat of the exhaust air. The enthalpy wheel contains a heat conducPng material and an opPonal discussant material to recover both sensible and latent heat energy. The funcPonality of the system is simple: a huge wheel rotates, capturing heat energy from the exhaust air and transferring it over to the outdoor air coming in. Figure 3 shows an image of how a heat recovery wheel works.

Figure 3. Heat Recovery Wheel.



Heat Pump System

The heat pump system in the HSS River Building provides simultaneous cooling and heaPng in occupant spaces depending on the needs of the occupant. In order to do so, the heat pump loop maintains a delicate temperature range by rejecPng or absorbing heat from a cooling tower and heat exchanger respecPvely. The current method of heat rejecPon is by a cooling tower on the roof spraying water and blasPng air in order to bring down the temperature to that of the loops. This method requires intense energy use by pumps and fans. The River Building is also being built next to the East River, a Pdal strait with a semi constant water temperature. With this being said, the proposed alternaPve redesign is to take advantage of the site and use the river as a heat rejecPon source rather than a cooling tower, reducing energy costs and equipments.

The system for using natural bodies of constant temperature for heat rejecPon is common in heat pump systems. Besides rivers, other thermal bodies such as underground soil, lakes, and ponds can be used as a heat rejecPon and absorpPon source. This can be achieved as the thermal body acts as a reservoir to supply or absorb the energy coming from the heat pump loop. Figure 4 shows how a body of water can act as a heat absorber.

Figure 4. Heat pump system using a pond as a source of heat rejecQon.



Proposal Breadth Topics

Along with the redesign of mechanical systems in the building, many other building systems are affected by the change. The proposal breadth topics will invesPgate the structural and architectural systems that will be affected by the mechanical design. Below are the proposed areas of breadth topics and a descripPon of how each will be approached.

Structural Proposal

By changing the 100% OA AHU and providing a heat recovery wheel, many mechanical equipments will be changed and even be removed from the schedule. Due to this alteraPon, the total weight of the penthouse will be changed and will perhaps reduce the amount of steel needed for support.

This will be accomplished with hand calculaPons and also the help of RAM, structural engineering soaware that will model the building’s structural system with the given structural plans provided by Cannon Design. The informaPon gathered from mechanical equipment specificaPons will be inpu>ed into RAM to help determine the steel sizes.

Architectural Proposal

The HSS River Building façade contains over 60% of glass as analyzed in Technical Assignment 2 – Building and Plant Energy Analysis Report. This high percentage of glass will increase solar heat gain and heat loss during the summer and winter Pmes respecPvely. A breadth analysis will determine whether or not the aid of solar shades or a façade with a different material will reduce internal loads, reducing the amount of energy needed to condiPon the building.

This will be accomplished by researching different solar shade products available on the market today and also by researching other materials that will decrease the heat transfer of the glass. This modeling will be performed on Trane Trace, a building energy modeling soaware that will calculate the new facades impact on internal loads. Also, Adobe Photoshop and Autodesk Revit will help provide renderings and models of the new façade appearance. This breadth will be analyzed before the mechanical changes occur in order to have the energy savings from the façade change be carried over in analysis of the new system.

Finally, these two breadth proposals will be analyzed with their associated costs and it will be determined whether or not significant savings will occur or if the addiPonal cost is worth the alteraPons.



Project Methods

Two alternaPve mechanical designs have been developed along with two breadth topics in the structural and architectural sides for the proposal. In order to analyze and determine the results, a well organized method needs to be developed for the spring 2008 semester.

In the Pme span of four months, the mechanical proposal will be carefully examined first by researching product designs and previous research and job projects relaPng to the topic. Aaer the research, a thorough analysis and modeling will be pursued by hand calculaPons and the aid of Trane Trace, an energy modeling soaware. This method will be used to analyze the proposed heat recovery wheel and heat rejecPon to the East River proposals. InformaPon that needs to be gathered that will be useful to assess the new proposal would be:

• River water temperature, rate of flow.

• Cost and amount of addiPonal pump and piping needed.

• Amount of exhaust air exhausted, temperatures and humidity.

• Cost of enthalpy wheel, space requirements.

Once the architectural breadth redesign has been developed and wri>en, a careful study of the mechanical redesign has been developed and wri>en along with the structural breadth. Using the same approach as with the mechanical redesign, the breadth topics will first involve research in products available and previous research and jobs on the topics. Then, a thorough analysis and modeling will be performed by hand calculaPons and the aid of Trane Trace. For the structural breadth, RAM, a structural design soaware, will be used to help calculate the new lower dead load of the mechanical equipments. And lastly for the architectural breadth, Adobe Photoshop and Autodesk Revit will be used for renderings and models of the new façade along with Trane Trace for load calculaPons. InformaPon that needs to be gathered that will be useful to assess the new breadth proposals would be:

• U‐values, shading coefficients, and area of fenestraPon of window s.

• Weight of each mechanical equipment in the penthouse mechanical room.

Throughout both the mechanical and breadth proposal analysis, a faculty consultaPon will occur during the later phase of the design porPon. This is to ensure that the design analysis is as accurate as possible and also provide helpful feedback to the redesign. Aaer the meePng takes place, several days will be designated for incorporaPng the feedback into the design.



Lastly, for all proposals a careful life cycle cost analysis will be performed. This will determine whether or not if the redesign is economically feasible or not.

Spring Semester Proposed Schedule

The following calendars are the proposed schedule that will be followed for the redesign of the mechanical system and the breadth topics. This is only an esPmate and does not contain daily details but rather how long each phase of the project will last. ModificaPons may occur due to unforeseen academic course load or personal events.



References

Chien, Maxwell. Technical Assignment 1 – ASHRAE Standard 62.1‐2007. 5 Oct. 2007. <h>p://www.engr.psu.edu/ae/thesis/poroolios/2008/mxc533/pdf/TechOneMaxwellChien.pd>

Chien, Maxwell. Technical Assignment 2 – Building and Plant Energy Analysis Report. 29 Oct. 2007.< h>p://www.engr.psu.edu/ae/thesis/poroolios/2008/mxc533/pdf/Tech_2_Maxwell‐Chien.pdf> Chien, Maxwell. Technical Assignment 3 ‐ Mechanical Systems ExisPng CondiPons EvaluaPon. 3 Dec. 2007. <h>p://www.engr.psu.edu/ae/thesis/poroolios/2008/mxc533/pdf/Tech_3_Maxwell‐Chien.pdf>